A polyimide resin having excellent heat resistance, electrical properties, mechanical properties or the like has been used for a surface protective film and interlayer insulating film of a semiconductor element. However, improvement of properties such as thermal cycle resistance and thermal shock resistance has been required due to high integration and growth in size of the semiconductor element, thickness reduction and miniaturization of an encapsulation resin package, and shift to surface mounting by solder reflow in recent years, and a polyimide resin having higher performance has been required.
On the other hand, attention has been focused on a technique for imparting photosensitivity to the polyimide resin itself. Examples of photosensitive polyimide resins include one represented by the following formula (8).

The use thereof allows simplification of a part of a pattern producing process, resulting in shortening the process. However, since solvents such as N-methyl-2-pyrrolidone are required for the development, there are problems in safety and handling. Consequently, a positive photosensitive resin developable in an alkaline water solution has been recently developed. For example, a positive photosensitive resin composed of a polybenzoxazole precursor and a diazoquinone compound has been disclosed (for example, see patent document 1). This has high heat resistance, excellent electrical properties and fine processability, and has a possibility not only as a resin for wafer coat but also as a resin for interlayer insulation. Referring to the development mechanism of this positive photosensitive resin, the diazoquinone compound of a non-exposure part is insoluble in the alkaline water solution. The chemical reaction of the diazoquinone compound is caused by exposure, and thereby the diazoquinone compound becomes soluble in the alkaline water solution. The coat pattern of only the non-exposure part can be produced by using a difference between solubility in the exposure part and that in the non-exposure part.
When these photosensitive resins are actually used for products, the adhesion between the photosensitive resin and encapsulation resin becomes important. Since these mainly act as a permanent protective film for interlayer insulation, and exist between the circuit element and the encapsulation resin, poor adhesion of the photosensitive resin and encapsulation resin causes a problem in the generation of peelings at the interface, resulting in a lack of practicality.
In recent years, growth in size and thickness reduction of a wafer has been particularly advanced, and 300 mm wafers have been used. When a conventional photosensitive resin is used, bending is often generated in the large wafers, and there exists a problem in that wafers are broken in a process for grinding a backside of the wafers to make them thinner. Therefore, means for solving such problems has been required.
Patent Document 1: Japanese Patent Publication No. 1-46862 B